Signal processor and signal processing method

ABSTRACT

A signal processor includes a memory storing instructions and a processor that implements the stored instructions to execute a plurality of tasks, the tasks including a first input task configured to obtain a first audio signal of a first channel, a second input task configured to obtain a second audio signal of a second channel, a first signal processing task configured to perform a first signal processing on the input first audio signal, a second signal processing task configured to perform a second signal processing on the input second audio signal, and a control task configured to, when the second input task does not obtain the second audio signal, cause the second signal processing task to perform the second signal processing on the input first audio signal having undergone the first signal processing by the first signal processing task.

CROSS REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority ofJapanese Patent Application No. 2019-072887 filed on Apr. 5, 2019, thecontents of which are incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

An embodiment of this invention relates to signal processing of an audiosignal.

2. Description of the Related Art

Recently, an audio signal processor has been present in whichmultichannel audio signals are inputted, signal processing is performedon the audio signals by a signal processing portion and the audiosignals having undergone the signal processing are outputted from aplurality of speakers (for example, see JP-A-2017-212573).

In a signal processor that performs signal processing for each channel,there are cases where a channel where no audio signal is inputted ispresent. That is, in a case where the number of inputted audio signalsis smaller than the number of channels, a signal processing portion anda memory corresponding to an audio signal of an unused channel arepresent. In this case, the resource for the audio signal of the unusedchannel is a waste.

SUMMARY OF THE INVENTION

Accordingly, an object of an embodiment of this invention is to enableeffective use of the resource of the unused channel.

A signal processor according to an aspect of the present inventionincludes a memory storing instructions and a processor that implementthe stored instructions to execute a plurality of tasks, the tasksincluding a first input task configured to obtain a first audio signalof a first channel, a second input task configured to obtain a secondaudio signal of a second channel, a first signal processing taskconfigured to perform a first signal processing on the input first audiosignal, a second signal processing task configured to perform a secondsignal processing on the input second audio signal, and a control taskconfigured to, in case where the second input task does not obtain thesecond audio signal, cause the second signal processing task to performthe second signal processing on the input first audio signal havingundergone the first signal processing by the first signal processingtask.

According to the aspect of the present invention, the resource for anaudio signal of an unused channel can be effectively used.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a structure of a principal part of asignal processor.

FIG. 2 is a view showing the relation of connection between an inputunit and a signal processing unit.

FIG. 3 is the relation of connection between the input unit and thesignal processing unit and is a view showing an example different fromthat of FIG. 2.

FIG. 4 is a flowchart showing an example of the operation of the signalprocessor.

FIG. 5 is a flowchart showing an example of object extractionprocessing.

FIG. 6 is a flowchart showing an example of signal processing.

FIG. 7 is a view showing an example of signal processing of acomparative example.

FIG. 8 is a view showing the relation of connection between an inputunit and a signal processing unit of a first modification.

FIG. 9 is a block diagram showing the structure of a principal part ofthe signal processor of second and third modifications.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

FIG. 1 is a block diagram showing a structure of a principal part of asignal processor 1. The signal processor 1 of the present embodimentwill be described with reference to the drawings.

The signal processor 1 is, for example, a personal computer, a set-topbox, an audio receiver or a powered speaker (a speaker with built-inamplifier). The signal processor 1 decodes contents data and extracts anaudio signal from the decoded contents data. The contents data isobtained from, for example, an external reproduction apparatus, anetwork or a storage medium. The signal processor 1 may obtain a digitalaudio signal or an analog audio signal.

In the present embodiment, if not specifically mentioned, the audiosignal means a digital signal.

As shown in FIG. 1, the signal processor 1 includes an input I/F(interface) 11, an object processing portion 12, an input unit 13, asignal processing unit 14, a localization processing portion 15, a D/Aconverter 16, an amplifier (AMP) 17, a CPU 18, a flash memory (ROM) 20,a RAM 19 and a bus 31. In this case, the bus 31 interconnects the inputI/F 11, the object processing portion 12, the input unit 13, the signalprocessing unit 14, the localization processing portion 15, the D/Aconverter 16, the amplifier (AMP) 17, the CPU 18, the flash memory 20and the RAM 19.

The CPU 18 integrally controls the signal processor 1. The CPU 18 readsa predetermined program stored in the flash memory 20 as a storage tothe RAM 19. Thereby, the CPU 18 performs various operations. The CPU 18referred to in this example corresponds to the control portion of thepresent invention. The RAM 19 referred to in this example corresponds tothe temporary storage of the present invention.

The input I/F 11 has an interface such as an HDMI (trademark). The inputI/F 11 receives contents data and outputs it to the object processingportion 12. Moreover, the input I/F 11 may receive a digital audiosignal or an analog audio signal.

The object processing portion 12 is configured by, for example, a DSP.In a case where the inputted contents data conforms to the object basemethod, the object processing portion 12 decodes the contents datareceived from the input I/F 11, and extracts the audio signal of eachobject (sound source) and position data representative of the positionof each object. According to the object base method, a plurality ofobjects (sound sources) contained in the contents are stored asindependent audio signals.

The object processing portion 12 assigns the extracted audio signals ofthe objects to a plurality of (in FIG. 2, four) channels. For example,in a case where audio signals of four objects are extracted, the objectprocessing portion 12 assigns the extracted four audio signals to afirst channel 121, a second channel 122, a third channel 123 and afourth channel 124.

In a case where the inputted contents data conforms to the channel basemethod, the object processing portion 12 analyzes the audio signalsinputted from the input I/F 11, and extracts the position data of theobjects. The object processing portion 12 calculates the level of theaudio signal of each channel and the cross-correlation between thechannels. The object processing portion 12 estimates the position of thesound source based on the level of the audio signal of each channel andthe cross-correlation between the channels. For example, in a case wherethe correlation value between the L channel and the SL channel is highand the level of the L channel and the level of the SL channel are high(exceed a predetermined threshold value), the object processing portion12 estimates that a sound source is present between the L channel andthe SL channel. The object processing portion 12 estimates the positionof the sound source based on the level of the L channel and the level ofthe SL channel. For example, when the ratio between the level of the Lchannel and the level of the SL channel is 1:1, the object processingportion 12 estimates that the position of the sound source is just atthe middle point between the L channel and the SL channel. The largerthe number of channels is, the more accurately the object processingportion 12 can estimate the position of the sound source. By calculatingthe correlation value between a multiplicity of channels, the objectprocessing portion 12 can substantially uniquely identify the positionof the sound source.

Moreover, the object processing portion 12 inputs the position data ofthe object to the CPU 18.

In the following description, the first channel 121, the second channel122, the third channel 123 and the fourth channel 124 will becollectively referred to as channels 121 to 124.

The input unit 13 and the signal processing unit 14 are configured by aDSP 10. The input unit 13 receives the audio signals assigned to thechannels 121 to 124 by the object processing portion 12. The signalprocessing unit 14 performs digital signal processing on the audiosignals inputted from the input unit 13 by frame processing. The signalprocessing unit 14 inputs the audio signals of the objects havingundergone the signal processing to the localization processing portion15. Details of the input unit 13 and the signal processing unit 14 willbe described later.

The localization processing portion 15 is configured by, for example, aDSP. The localization processing portion 15 performs sound imagelocalization processing according to an instruction of the CPU 18. Thelocalization processing portion 15 performs sound image localization inunits of objects, based on the position data of each object obtained bythe object processing portion 12, so that the sound image is localizedin a position corresponding to the position data of each objectspecified by the CPU 18. The localization processing portion 15distributes the audio signal of each object to a plurality of speakerswith a predetermined gain so that the sound image is localized in aposition corresponding to the position information of each object. Thelocalization processing portion 15 inputs the audio signals for thespeakers to the D/A converter 16.

The plurality of speakers are placed, for example, indoors (in a room).For example, when the shape of the room is a rectangular parallelepiped,the four speakers are placed in the four corners of the floor of theroom, respectively. Moreover, for example, another speaker is placed atthe front of the room. Moreover, for example, other two speakers areplaced on the ceiling in the room.

The shape of the room is not limited to a rectangular parallelepiped. Itis necessary only that the plurality of speakers be placed according tothe shape of the room.

The D/A converter 16 converts the audio signals into analog signals. TheAMP 17 amplifies the analog audio signals, and inputs them to thespeakers.

In this example, the input unit 13 and the signal processing unit 14receive audio signals of objects of up to four channels, and performsignal processing on the audio signals.

Details of the input unit 13 and the signal processing unit 14 will bedescribed with reference to FIG. 2. FIG. 2 is a view showing therelation of connection between the input unit 13 and the signalprocessing unit 14.

As shown in FIG. 2, the input unit 13 includes a first input portion131, a second input portion 132, a third input portion 133 and a fourthinput portion 134. The first input portion 131, the second input portion132, the third input portion 133 and the fourth input portion 134 willbe collectively referred to as input portions 131 to 134.

The first input portion 131 receives the audio signal of the firstchannel 121. The second input portion 132 receives the audio signal ofthe second channel 122. The third input portion 133 receives the audiosignal of the third channel 123. The fourth input portion 134 receivesthe audio signal of the fourth channel 124.

The signal processing unit 14 includes a first signal processing portion141, a second signal processing portion 142, a third signal processingportion 143 and a fourth signal processing portion 144. The first signalprocessing portion 141, the second signal processing portion 142, thethird signal processing portion 143 and the fourth signal processingportion 144 will be collectively referred to as signal processingportions 141 to 144.

The first signal processing portion 141 performs signal processing onthe audio signal of the first channel 121 inputted from the first inputportion 131. The second signal processing portion 142 performs signalprocessing on the audio signal of the second channel 122 inputted fromthe second input portion 132. The third signal processing portion 143performs signal processing on the audio signal of the third channel 123inputted from the third input portion 133. The fourth signal processingportion 144 performs signal processing on the audio signal of the fourthchannels 124 inputted from the fourth input portion 134.

The signal processing portions 141 to 144 perform signal processing ofthe audio signals of a plurality of (four) channels 121 to 124 for eachone frame. The CPU 18 previously allocates the RAM 19 for the resourceof this one frame.

In this example, the signal processing portions 141 to 144 each performsignal processing of delay, equalizer (EQ) and reverb, which are threekinds of effects, on the audio signal of each object. In this example,the kinds and number of effects of the signal processing of each of thesignal processing portions 141 to 144 are the same.

The signal processing portions 141 to 144 each perform signal processingof the audio signal of each of the four channels 121 to 124, and outputthese audio signals to the localization processing portion 15.

Now, a case where the input I/F 11 inputs contents data containing audiosignals of two objects will be described with reference to FIG. 3. FIG.3 is the relation of connection between the input unit 13 and the signalprocessing unit 14. The example of FIG. 3 shows a case where the numberof audio signals extracted by the object processing portion 12 issmaller than the number of channels 121 to 124.

The object processing portion 12 extracts the audio signal of eachobject from the contents data. The audio signal extracted by the objectprocessing portion 12 is assigned to the first channel 121 and the thirdchannel 123. The object processing portion 12 does not input the audiosignal to the second channel 122 or the fourth channel 124. That is, inthis example, the second channel 122 and the fourth channel 124 are notused. The object processing portion 12 further extracts the positiondata of the object of the extracted audio signal.

In this case, the signal processor 1 causes the second signal processingportion 142 corresponding to the unused second channel 122 to processthe audio signal assigned to the first channel 121. Moreover, the signalprocessor 1 causes the fourth signal processing portion 144corresponding to the unused fourth channels 124 to process the audiosignal assigned to the third channel 123.

In more detail, as shown in FIG. 3, the CPU 18 connects an output end 41on the output side of the first signal processing portion 141 to aninput end 42 on the input side of the second signal processing portion142. Further, the CPU 18 connects an output end 43 on the output side ofthe third signal processing portion 143 to an input end 44 on the inputside of the fourth signal processing portion 144.

Thereby, the audio signals of the first channel 121 and the thirdchannel 123 enjoy effects of signal processing of two delays, twoequalizers and two reverbs. Since the signal processing portions 141 to144 are processing within one frame, it is unnecessary to increaseresources even if the audio signals of the first channel 121 and thethird channel 123 process signal processing of two delays, two EQs andtwo reverbs.

For example, for the audio signal of the first channel 121, by using thereverb of the second signal processing portion 142, twice the length(tap length) can be realized within one frame compared with a case wherethe second signal processing portion 142 is not used. Therefore, by theaudio signals of the first channel 121 and the third channel 123 usingthe signal processing of two delays, two EQs and two reverbs incombination, the signal processor 1 can perform a variety of expressionswith already secured resources, for example, with allocated memory andan redundant capability of the CPU.

The signal processing unit 14 outputs the signal-processed audio signalof the first channel 121 to the localization processing portion 15 fromthe output side of the second signal processing portion 142. Moreover,the signal processing unit 14 outputs the signal-processed audio signalof the third channel 123 to the localization processing portion 15 fromthe output side of the fourth signal processing portion 144.

An example of the operation of the signal processor 1 will be describedwith reference to FIGS. 4, 5 and 6. FIG. 4 is a flowchart showing theexample of the operation of the signal processor 1. FIG. 5 is aflowchart showing an example of object extraction processing by theobject processing portion 12. FIG. 6 is a flowchart showing an exampleof signal processing by the signal processing unit 14. In the following,description will be given with respect to a case where contents datacontains audio signals of four objects and a case where it containsaudio signals of two objects.

When the input I/F 11 inputs contents data (S11: Yes), the objectprocessing portion 12 performs object extraction processing (S12). Whenthe object processing portion 12 finishes the object extractionprocessing, the signal processing unit 14 performs signal processing(S13). When the signal processing unit 14 finishes the signalprocessing, sound image localization by the localization processingportion 15 is performed (S14).

The object extraction processing will be described with reference toFIG. 5. The object processing portion 12 extracts the audio signal ofeach object from the contents data (S21). When the number (four) ofaudio signals of the objects is the same as the number (four) ofchannels (S22:Yes), the object processing portion 12 assigns theextracted four audio signals to the four channels 121 to 124 (S23). Theobject processing portion 12 inputs the audio signals assigned to thefour channels 121 to 124, respectively, to the corresponding inputportions 131 to 134 (S24). The object processing portion 12 extracts theposition data of each object (S25).

On the other hand, when the number (two) of audio signals is differentsmaller) from the number (four) of channels (S22: No), the objectprocessing portion 12 assigns the extracted two audio signals to thefirst channel 121 and the third channel 123, respectively (S26). Theobject processing portion 12 shifts the process to S24. In this case,the second input portion 132 and the fourth input portion 134 input noaudio signals.

The position data extraction (S25) may be performed at any timing aslong as it is performed after the extraction of the audio signals by theobject processing portion 12. Moreover, a structure may be adopted inwhich the object processing portion 12 automatically assigns theextracted two audio signals to the first channel 121 and the thirdchannel 123, respectively. Moreover, the object processing portion 12may assign the extracted two audio signals to the first channel 121 andthe third channel 123, respectively, according to external setting, forexample, setting by the user.

The signal processing will be described with reference to FIG. 6. Whenthe second input portion 132 and the fourth input portion 134 haveinputted audio signals (S31: Yes, S32: Yes), the plurality of signalprocessing portions 141 to 144 perform the signal processing on theaudio signals inputted from the plurality of input portions 131 to 134,respectively (S33). The signal processing portions 141 to 144 eachoutput the signal-processed audio signal to the localization processingportion 15 (S34).

On the other hand, when the second input portion 132 has inputted noaudio signal (S31: No), the CPU 18 connects the first signal processingportion 141 and the second signal processing portion 142 (S35) together.Moreover, when the fourth input portion 134 has inputted no audio signal(S32: No), the CPU 18 connects the third signal processing portion 143and the fourth signal processing portion 144 together (S36). The signalprocessing unit 14 shifts the process to S33. In this case, the signalprocessing unit 14 outputs the signal-processed audio signals to thelocalization processing portion 15 from the second signal processingportion 142 and the fourth signal processing portion 144 (S34).

A structure may be adopted in which the CPU 18 automatically connectsthe first signal processing portion 141 and the second signal processingportion 142 together. Moreover, the CPU 18 may connect the first signalprocessing portion 141 and the second signal processing portion 142together according to external setting, for example, setting by theuser.

For example, in a conventional signal processor of a comparativeexample, as shown in FIG. 7, a next frame is newly added in order toincrease signal processing (for example, the number of effects) of adesired audio signal. In the signal processor of the comparativeexample, the addition of the next frame makes it necessary to secure anew resource in the RAM. As described above, in the conventional signalprocessor of the comparative example, since the CPU causes the RAM tosecure a new resource, the capacity of the RAM used increases and thetime required for the signal processing increases, so that an outputdelay occurs.

On the other hand, in a case where it is intended to increase the signalprocessing (for example, the number of effects) of the audio signal ofthe first channel 121, if the second channel 122 is not used, the signalprocessor 1 of the present embodiment performs the signal processing ofthe first signal processing portion 141 and the second signal processingportion 142 on the audio signal of the first channel 121 in the order ofthe signal processing of the first signal processing portion 141 and thesignal processing of the second signal processing portion 142. Moreover,in a case where it is intended to increase the signal processing (forexample, the number of effects) of the audio signal of the third channel123, if the fourth channel 124 is not used, the signal processor 1performs the signal processing of the third signal processing portion143 and the fourth signal processing portion 144 on the audio signal ofthe third channel 123 in the order of the signal processing of the thirdsignal processing portion 143 and the signal processing of the fourthsignal processing portion 144.

In the signal processor 1 of the present embodiment, signal processingin one frame is performed in the order of the first signal processingportion 141, the second signal processing portion 142, the third signalprocessing portion 143 and the fourth signal processing portion 144 (seeFIG. 2). That is, for example, if the output side of the second signalprocessing portion 142 and the input side of the first signal processingportion 141 are connected together and the processing is performed inthe order of the second signal processing portion 142 and the firstsignal processing portion 141, the signal processing is the same as theone of the conventional signal processor (see FIG. 7).

Thereby, in the signal processor 1 of the present embodiment, since aresource, for example, an allocated memory and an redundant capabilityof the CPU, is previously secured so that signal processing can beperformed in one frame on the audio signals of the channels 121 to 124,the signal processing portions for unused channels can be effectivelyused.

Moreover, the signal processor 1 of the present embodiment processes theaudio signals in one frame. Thereby, the signal processor 1 of thepresent embodiment does not cause a delay due to increase in signalprocessing compared with the signal processor of the comparativeexample. Moreover, since the signal processor 1 of the presentembodiment does not cause a delay due to increase in signal processing,real-time property does not deteriorate.

The localization processing portion 15 of the signal processor 1 of thepresent embodiment is not an essential element in the present invention.

Modifications

The signal processor 1 of a first modification will be described withreference to FIG. 8. The signal processor 1 of the modification is anexample in which contents data containing an audio signal of one objectis inputted. Description of the elements the same as those of the signalprocessor 1 of the above-described embodiment is omitted.

FIG. 8 is a view showing the relation of connection between the inputunit 13 and a signal processing unit 14A of the first modification.

As shown in FIG. 8, the first input portion 131 of the input unit 13 ofthe first modification inputs the audio signal of the first channel 121.The second input portion 132, the third input portion 133 and the fourthinput portion 134 input no audio signal. That is, in this example, thesecond channel 122, the third channel 123 and the fourth channel 124 arenot used.

The CPU 18 causes the second signal processing portion 142, the thirdsignal processing portion 143 and the fourth signal processing portion144 to process the audio signal of the first channel 121.

In more detail, the CPU 18 connects the output end 41 on the output sideof the first signal processing portion 141 and the input end 42 on theinput side of the second signal processing portion 142 together.Moreover, the CPU 18 connects an output end 45 on the output side of thesecond signal processing portion 142 and an input end 46 on the inputside of the third signal processing portion 143 together. Further, theCPU 18 connects an output end 43 on the output side of the third signalprocessing portion 143 and an input end 44 on the input side of thefourth signal processing portion 144 together.

The first signal processing portion 141 inputs the audio signals of thefirst input portion 131 to the first channel 121. The signal processingportions 141 to 144 perform signal processing of the audio signal of thefirst channel 121. The signal processing unit 14A outputs thesignal-processed audio signal to the localization processing portion 15from the fourth signal processing portion 144.

As described above, the signal processing unit 14A of the signalprocessor 1 of the first modification can perform signal processing ofthe signal processing portions 141 to 144 on the audio signal of thefirst channel 121. That is, if the number of audio signals is smallerthan the number of channels, processing can be increased by using thesignal processing portion corresponding to the unused channel. In thiscase also, in the signal processor 1 of the first modification in whichsignal processing is performed in one frame, resources can beeffectively used and no delay is caused.

Consequently, with the signal processor 1 of the first modification, byusing a multiplicity of effects on the audio signal of the first channel121, more diverse expressions can be performed with already securedresources.

A signal processor 1A of a second modification will be described withreference to FIG. 9. FIG. 9 is a block diagram showing the structure ofa principal part of the signal processor 1A of the second modification.The signal processor 1A of the second modification is different from thesignal processors 1 of the above-described embodiment and the firstmodification in that a user interface (I/F) 21 and a display portion 22are further provided. Description of the elements the same as those ofthe signal processor 1 of the above-described embodiment is omitted.

The display portion 22 is a display device that causes a display device(not shown) to display an unused channel, for example, a monitor of apersonal computer.

Moreover, the user I/F 21 is provided with a signal input instructionbutton (not shown) and the like for each of a plurality of channels 121to 124. For example, in a case where the second channel 122 is not used,when the user depresses the signal input instruction buttoncorresponding to the second channel 122, the CPU 18 causes the secondsignal processing portion 142 corresponding to the unused second channel122 to process the audio signal of the first channel 121.

Thereby, the signal processor 1A of the second modification can graspthe channel not used by the user through the display portion 22.Moreover, the signal processor 1A of the second modification caneffectively use the resource for the audio signal of the unused channelaccording to an instruction of the user. Further, since the signalprocessor 1A of the second modification processes the audio signal inone frame, even when the user I/F 21 accepts an instruction from theuser, deterioration of real-time property can be reduced.

The user I/F 21 may be connected to a user operable external devicewirelessly or by wire.

Moreover, the display portion 22 is, for example, a display configuredby laminated touch panels, and may display a GUI (graphical userinterface) screen for accepting operations by the user. In this case,the display portion 22 displays a signal input instruction button on theGUI screen, and the user I/F 21 accepts an instruction according to theuser's operation.

Moreover, the signal processor 1A of the second modification may be usedin combination with the signal processor 1 of the first modification.

The signal processor 1A of a third modification will be described withreference to FIG. 9. Description of the elements the same as those ofthe signal processor 1 of the above-described embodiment is omitted.

In the signal processor 1A of the third modification, the sound imageposition of the object is changed by an instruction of the user. In thiscase, the user I/F 21 accepts a change instruction by the user using theGUI screen (not shown). On the GUI, for example, an imitative viewshowing the room and the positions of the speakers is shown. That is, bythe user touching or swiping the place where the user intends to changethe sound image position on the GUI, the user I/F 21 accepts the soundimage position change instruction and change position. The CPU 18distributes the audio signal of the objects to the speakers with apredetermined gain so that the sound image is localized according to thechanged position.

The signal processor 1A of the third modification may use the signalprocessors 1 and 1A of the first and second modifications incombination.

Thereby, with the signal processor 1A of the third modification, thesound image position can be changed by the user.

The programs executed in the present embodiment and the modificationsare not necessarily stored in the flash memory 20 of the own devices.For example, the signal processors 1 and 1A may download programs fromanother device such as a server as appropriate and read them to the RAM19.

Moreover, the signal processors 1 and 1A of the present embodiment andthe modifications are described with respect to the examples providedwith four channels, the present invention is not limited thereto. Thesignal processors 1 and 1A of the present invention may be structured soas to be provided with less than four channels and perform signalprocessing of the audio signals of these channels in one frame.Moreover, the signal processor 1 of the present invention may bestructured so as to be provided with more than four channels and performsignal processing of the audio signals of these channels in one frame.

Moreover, the kinds of signal processing of the first signal processingportion 141 may be different from those of the second signal processingportion 142. In this case, for example, for the first signal processingportion 141, an effect such as chorus may be added besides delay, EQ andreverb.

Doing this enables the signal processors 1 and 1A of the presentembodiment and the modifications to perform a wide variety ofexpressions with already secured resources.

The descriptions of the present embodiment should be consideredillustrative in all respects and not restrictive. The scope of thepresent invention is shown not by the above-described embodiment but bythe scope of the claims. Further, it is intended that all changes withinthe meaning and the scope equivalent to the scope of the claims areembraced by the scope of the present invention.

What is claimed is:
 1. A signal processor comprising: a memory storinginstructions; and a processor that implements the stored instructions toexecute a plurality of tasks, including: a first input task configuredto obtain a first audio signal of a first channel; a second input taskconfigured to obtain a second audio signal of a second channel; a firstsignal processing task configured to perform a first signal processingon the input first audio signal; a second signal processing taskconfigured to perform a second signal processing on the input secondaudio signal; and a control task configured to, in case where the secondinput task does not obtain the second audio signal, cause the secondsignal processing task to perform the second signal processing on theinput first audio signal having undergone the first signal processing bythe first signal processing task.
 2. The signal processor according toclaim 1, wherein the plurality of tasks further include: a third inputtask configured to obtain a third audio signal of a third channel; and athird signal processing task configured to perform a third signalprocessing on the input third audio signal, wherein the control task, ina case where the third input task does not obtain the third audiosignal, causes the third signal processing task to perform the thirdsignal processing on the input first audio signal having undergone boththe first signal processing and the second signal processing.
 3. Thesignal processor according to claim 1, wherein the plurality of tasksfurther include an object processing task configured to extract an audiosignal of each object from contents data and assign the extracted audiosignal of each object to the first channel or the second channel.
 4. Thesignal processor according to claim 3, wherein the plurality of tasksfurther include a localization processing task configured to performsound image localization of each object based on position dataindicating a position of the respective object obtained by the objectprocessing task.
 5. The signal processor according to claim 1, wherein akind of the first signal processing is the same as that of the secondsignal processing.
 6. The signal processor according to claim 1, whereina kind of the first signal processing is different from that of thesecond signal processing.
 7. The signal processor according to claim 1,wherein: the plurality of tasks further include a temporary storing taskconfigured to temporarily store information in a temporary storage,wherein the control task allocates the temporary storage in advance fora resource of the first signal processing and a resource of the secondsignal processing.
 8. The signal processor according to claim 1, whereinthe control task causes the first signal processing task and the secondsignal processing task to perform a plurality of kinds of signalprocessing.
 9. The signal processor according to claim 1, furthercomprising: a user interface configured to accept a signal inputinstruction from a user, wherein, upon the user interface accepting thesignal input instruction, the control task restricts inputting of thesecond audio signal for the second signal processing by the secondsignal processing task, and causes the second signal processing task toperform the second signal processing on the input first audio signalhaving undergone the first signal processing.
 10. The signal processoraccording to claim 1, wherein the second signal processing task performsthe second signal processing on the input first audio signal after thefirst signal processing task performs the first signal processing on theinput first audio signal for each frame.
 11. A signal processing methodfor a signal processor including an input interface for inputting anaudio signal, the signal processing method comprising: obtaining a firstaudio signal of a first channel input to the input interface; obtaininga second audio signal of a second channel input to the input interface;performing a first signal processing on the input first audio signal;performing a second signal processing on the input second audio signal;and performing, in case where the second audio signal is not obtained,the second signal processing on the input first audio signal havingundergone the first signal processing.
 12. The signal processing methodaccording to claim 11, further comprising: obtaining a third audiosignal of a third channel input to the input interface; performing athird signal processing on the input third audio signal; and performing,in a case where the third audio signal is not obtained, the third signalprocessing on the first audio signal having undergone both the firstsignal processing and the second signal processing.
 13. The signalprocessing method according to claim 11, further comprising: extractingan audio signal for each object from content data; and assigning theextracted audio signal of each object to the first channel or the secondchannel.
 14. The signal processing method according to claim 13, furthercomprising performing sound image localization of each object based onposition data indicating a position of the obtained respective object.15. The signal processing method according to claim 11, wherein a kindof the first signal processing is the same as that of the second signalprocessing.
 16. The signal processing method according to claim 11,wherein a kind of the first signal processing is different from that ofthe second signal processing.
 17. The signal processing method accordingto claim 11, further comprising allocating a temporary storage inadvance for a resource of the first signal processing and a resource ofthe second signal processing, to temporarily store information.
 18. Thesignal processing method according to claim 11, wherein the first signalprocessing and the second signal processing each perform a plurality ofkinds of signal processing.
 19. The signal processing method accordingto claim 11, further comprising: accepting a signal input instruction bya user using a user interface; restricting, upon the user interfaceaccepting the signal input instruction, inputting of the second audiosignal for the second signal processing portion, and causing the secondsignal processing to perform the second signal processing on the inputfirst audio signal having undergone the first signal processing.
 20. Thesignal processing method according to claim 11, wherein the secondsignal processing is performed on the input first audio signal afterperforming the first signal processing on the input first audio signal.